1. Field of the Invention
This invention relates to digital television systems, more particularly to special features for digital television systems.
2. Background of the Invention
Digital television has several advantages over the current standard analog system. Because the digital data can be packed, more data can be transmitted that allows for a better picture. Additionally, manipulation of the data on a picture element (pixel) level can reduce artifacts and increase the resolution and overall clarity of the picture.
Currently, most televisions that implement digital displays remain restricted by the analog transmission standard. Because of that and because, to some extent, adding special features in analog requires less data manipulation, most of these sets do all of the processing in the analog realm and convert to digital just before display.
While some special feature processing modules process data in the digital realm internally, most have analog input and output (I/O) to support analog broadcast and display standards. These processing modules must then include an analog to digital (A/D) converter for the inputs and a digital to analog (D/A) converter for the outputs. This increases the complexity and cost of the processing circuitry over a circuit with digital I/O. Further, each converter degrades the digital signal. For televisions that implement digital displays and several special feature modules, this series of AIDs and D/As can noticeably corrupt the television picture.
Special features include picture-in-picture (PIP), which allows other channels to be viewed within the main channel's picture. These usually reside in small windows around the outside of the main channel's picture, or the channel being viewed. Picture-outside-picture typically has the extra channels along the side, top or bottom of the main channel, but instead of encroaching on the main channel's picture, they are boxed next to it. Additional special features are zoom, freeze, TV guide and his/hers. TV guide usually involves some number of channels all displayed simultaneously, with no main channel picture, so the viewer can decide what to watch. His/hers includes two pictures, side by side on the TV.
Most current television systems perform the channel manipulation and set up in analog and then convert the incoming data to digital format for display. This becomes awkward when either the entire television system functions digitally, or the incoming signal is itself digital. Therefore, a need exists for the ability to provide the special features of a television set in the digital realm.